Electric heater



Dec. 6, 1927. 1,651,861

C- C. ABBOTT ELECTRIC HEATER Filed Oct. 17, 1922 Fig]. 23

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Patentetl Dec. e, 1927;"

UNITED STATES 1,651,861 PATENT OFFICE.

CHARLES C. ABBOTT, OF PITTSFIELD, MASSACHUSETTS, ASSIGNOR TO GENERAL ELEC- TRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC HEATER. 7

Application filed October 17, 1922. Serial No. 595,191.

My invention relates to electric heaters, more particularly to electric immersion heaters, and has for its object the provision of an improved electric heater of this type. In carrying out my invention I use an electric heating unit of the sheath wire type. In heating units of this type the resistance conductor is embedded in a compacted mass of insulating material enclosed by a metallic containing sheath. Such units throughout the length of the sheath are inherently im-- pervious to moisture, and they may beeasily bent to any desired form. They are therefore particularly adapted for use as immerl5 sion heaters. In one embodiment of my invention I use a helical core sheath wire heating unit, such asforming the subject matter of my copending application, Serial No. 549,636, filed April 4th, 1922. In carrying out my invention, I shape the heating unit in the preferred form and so that the ends of the heating unit from which the terminals project are adjacent each other, and embed the ends of the heating unit in a suitable insulating sealing material such that the heating unit is made moisture proof.

For a better understanding of my invention, reference should-be had to the accompanying drawings in which Fig. 1 is a view partly in section showing an immersion heater constructed in accordance with my invention; Fig. 2 is an elevation view of Fig.

1; whileFig. 3 is an enlarged partial sectional view showing the terminal arrangement at the ends of the heating unit.

Referring to the drawing, in one form of my invention the sheath wire heating unit 10 is shaped so as to have a central sinuous or coiled heating portion 11 and with the two end portions extending parallel with and adjacent to each other. The heating unit 10 is shown of the helical core sheath wire type, such as forming the subject matter of my aforesaid application, and comprises a resistance conductor 12 shaped in the form of a helix and embedded in heat refractory insulating material 13 compacted to a hard dense mass within a cylindrical metallic containing sheath 14. The insulating material but forms a good conductor of heat between the resistance conductor and the sheath. By shaping the resistanceconductor into a helix a much, greater heating effect may be ob-- tained for a given length than can be ob-' not only insulates the-resistance conductor tained with a straight resistance conductor. The sheath 14 is formed from a length of tubing, the insulating material being compacted by reducing the diameter of the sheath by swaging. The heating unit is therefore throughout its length completely impervious to moisture.

The helical resistance conductor 12 preferably extends through the central coiled or helical portion 11 only so vthat the heating effect is concentrated in this coiled portion. Connected to the ends of the resistance conductor are the metallic terminals 15, only one of which is shown. These terminals, which are in the form of rods, are embedded in the compacted insulating material 13 and are thus secured by the insulating material central of the sheath. As shown, the connection between the terminals and the resistance conductor is effected by threading the inner end of each terminal and screwing the con volutions of the resistance conductor onto this threaded portion 16. An insulating spacing washer 17 is provided on the inner end of each terminal whereby the inner ends of the terminals are positively centered in the sheath during the construction of the heating unit, as described and claimed in my copending application, Serial No. 595192, filed October 17 1922. The terminals extend centrally throughout the parallel portions of the sheath and project from the ends of the sheath.

Secured to the outer projecting ends of the terminals 15 are connecting lugs 18 made of a suitable electrically conducting material, such as brass. These lugs may be convenientlysecured, for example, as described and claimed in my aforesaid copending application, Serial No. 549,636, by providing recesses therein in which the terminals are inserted, the lugs then being compressed so as to force the material into nicks 19 previously formed in the ends of the terminals. The lugs are secured on the terminals a short distance from the adjacent ends of the heating unit, so as to leave an annular space 20 between each lug and the end of the heating unit. A short portion of the projecting end of each terminal 15 is, thus exposed.- Annular grooves 21 and 22- are provided on the ends of the heating unit and on the lugs respectively. Each lug is provided with a contact pro ection 18.

A metallic casing or receptacle 23, having an oblong cross sect-ion, is secured to the ends of the heating unit near the annular grooves 21, the ends of the heating unit being inserted through suitalole aperture in the bottom of the receptacle and the receptacle being secured to the sheath 14: by brazed or welded joints 2%. A suitable electrically insulating sealing compound or material 25, such as hakelite, is compressed while in a plastic condition into the receptacle around the grooved ends of the sheath, the exposed portions ot' the terminals, and the grooved portions of the lugs 18. This insulating material fills the grooves 21 and 22 and the spaces 20 between the lugs and the ends of the heating unit so as to embed the grooved ends of both the sheath and lu- 's and the exposed portions of the terminas, thus thoroughly sealing the ends of the heating unit against the entrance of moisture. The grooves 21 and 22 serve to anchor the sealing material and also to more efi'ective- 1y seal the heating unit by increasing the creeping surface for moisture. The receptacle 23 is of sufficient depth to extend around and protect the contact projections 18 and act as a connecting plug guide. The heater may be connected to a suitable source of electrical supply by means of a suitable plug connector adapted to he inserted in the receptacle and make an electrical connection with the two projections 18.

In using the heater the coiled. heating portion 11 is immersed in the liquid to be heated to a suitable depth, the receptacle 213 containing the electrical contacts being without the heated liquid. Since the heating efi'ect is concentrated in the coiled portion, the outer end of the heater'will not be heated to any considerable extent so that the sealing material will not be softened and the heater may be easily handled. The particular form of my invention shown is adapted for heating liquids in glasses, cups, etc.

While I have described my invention as embodied in concrete form andas operating in a specific manner in accordance with the provisions of the patent statutes, it should be understood that I do not limit my invention thereto, since various modifications esitant.

thereof will suggest themselves to those skilled in the art without departing :trom the spirit of my invention, the scope 0t which is set forth in the annexed claims.

What it claim as new and desire to secure by Letters Patent or" the United States, is:

T. An immersion heater comprising a metallic sheath formed with a central sinuous portion and having its ends adjacent each other, a receptacle secured to said sheath near its ends, an insulated resistance conduc terin said sheath having terminals projecting from the ends of said sheath, connecting lugs secured to said terminals in spaced relation with the ends of said sheath, the ends of said sheath and said lugs being provided with grooves, and an insulating sealing material in said receptacle fillinp said grooves.

2. An immersion heater comprising a me tallic sheath formed with a central sinuous portion and having parallel adjacent portions at its ends, an insulated resistance conductor in said sinuous portion terminating substantially at the junction of said sinuous portion and said end portion, insulated terminals connected to said resistance conductor extending throughout the lengths of said parallel end portions and projecting "from said sheath, and an insulating sealing material embedding said terminals and the ends oi" said sheath.

3. An immersion heater comprising a metallic sheath formed with a central sinuous portion and having parallel adjacent portions at its ends, an insulated resistance con d-uctor insaid sinuous portion, insulated terminals for said resistance conductor extending throughout the lengths of said parallel end portions and projecting from said sheath, the ends of said sheath and said terminals being provided with peripheral grooves, a receptacle secured to said sheath near its ends and an insulating sealing material in said receptacle embedding said sheath and said terminals and filling said grooves.

In witness whereof, I have hereunto set my hand this 13th day of October, 1922.

CHARLES C. ABBOTT. 

